Dec 3, 2013 - Grand Canyon, Arizona, U.S. - <br /> <br /> Rare Fog Engulfs Grand Canyon<br /> <br /> In a photo released by the National Park Service, tourists look out over a rare total cloud inversion at Grand Canyon National Park Friday. Cloud inversions are created through the interaction of warm and cold air masses.<br /> ©Erin Whittaker/Exclusivepix
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